Nickel electrodepositing baths,process,and additive composition comprising levelling agent therefor



United States Patent 90,780 ILLS. Cl. 204-49 lint. Cl. C23lo 5/08 16Claims ABSTRACT OF THE DISCLOSURE Aqueous acidic nickelelectrodepositing baths containing as levelling agent the condensationreaction product of naphtho-1,8-sultone with a heterocyclic aromaticcompound containing at least one five-membered heterocyclic ringincluding at least one ring nitrogen atom and at least one labilehydrogen atom. Such reaction product is prepared by heating an aqueousliquid admixture of the napthosultone and the heterocyclic aromaticcompound present in at least the stoichiometric amount under acidconditions to an elevated temperature below 65 C., maintaining theadmixture at the elevated temperature below 65 C. until thenaphthosultone dissolves in the aqueous liquid, then heating theresultant liquid solution to a reaction temperature above 65 C. butbelow 100 C., maintaining the solution at a reaction temperature above65 C. but below 100 C. until the viscosity of the liquid solutionincreases appreciably and the solution is of a syrupy consistency, andcooling the thus treated solution to ambient temperature.

This invention relates to novel condensation reaction products of anaphthosultone and a heterocyclic aromatic compound containing one ormore five-membered rings, and more especially to new and improved nickelelectrodepositing baths containing such condensation reaction productsas additives, novel compositions containing the condensation reactionproducts and especially well suited as levelling additives for thebaths, an improvement in the method for electrodepositing nickelinvolving the use of the novel baths herein, and the novel condensationreaction products per se.

Compounds obtained by the reaction of 1,3- or 1,4- sultones, especiallyof 1,3-propanesultone and of 1,4- butanesultone, with heterocyclictertiary amines of one or more six-membered aromatic rings are knownadditives for nickel electrodepositing baths. The application of suchcompositions for nickel electroplating is set forth in French Patent1,143,382, granted Mar. 14, 1956. In addition to 1,3-propanesultone and1,4-butanesultone, this patent also discloses as reactant sulfones suchas tolylsultone and naphtho-l,8-sultone. As the heterocyclic tertiaryamines of one or more six-membered rings as reactant, such patentdiscloses those containing a pyridine ring or a diazine ring, bothsix-membered aromatic ring compounds, with ultimately one or two benzenerings attached to the siX-membered heterocyclic ring and/or substituentsthereof.

Such known compounds or compositions, notably the reaction product ofpyridine or quinoline with propaneice sultone, impart a good levellingeifect on customary types of bright nickel plating baths, but theiraction diminishes rapidly and prematurely in the course of time and itis necessary to prematurely regenerate these compositions by prolongedheating of the electrolyte for several hours at 85 C. The necessity ofsuch regeneration is recognized in French Patent 1,324,768, granted June2, 1962. Further the addition of such compounds diminishes appreciablythe throwing power of the electrolyte, which is inconvenient when nickelplating articles of complex shape.

One object of this invention is to provide new and improved nickelelectrodepositing baths achieving a maxi mum levelling effect.

Another object is to provide new and improved nickel electroplatingbaths which are highly levelling without a significant reduction in thethrowing power of the bath.

Another object is to provide new and improved nickel electroplatingbaths characterized by providing a prolonged good levelling effectwithout the requirement of periodic regeneration of the baths by heatingor otherwise.

A further object is to provide novel condensation reaction products of anaphthosultone with a heterocyclic aromatic compound containing at leastone five-membered ring including one or more ring nitrogen atoms and oneor more labile, i.e., easily substitutable, hydrogen atoms.

A further object is to provide an improvement in the method forelectrodepositing of nickel characterized by providing maximum levellingof the nickel being deposited.

Another object is to provide new compositions containing the novelcondensation products herein, and which are eminently well suited foruse as levelling additives for nickel electroplating baths.

Still a further object is to provide a novel method for the preparationof the condensation reaction products herein.

Additional objects and advantages will be readily ap parent as theinvention is hereinafter described in detail.

In accordance with the present invention, it has been found that by theaddition to the prior nickel electrodepositing baths of thebath-compatible condensation reaction product of a naphthosultone, forinstance naphtho- 1,8-sultone, with a heterocyclic aromatic compoundcontaining at least one five-membered ring including one or more ringnitrogen atoms and one or more labile, i.e., easily substitutable orreplaceable, hydrogen atoms, nickel electrodepositing baths are obtainedwhich are highly levelling and without a significant reduction inthrowing power of the electrolyte. In addition, the compounds of theinvention are stable in the baths, which eliminates the requirement forperiodic treatment for regeneration which was necessary in the case ofthe heterocyclic hexagonal, i.e., six-membered ring, aromatic compoundsof the prior art.

The novel condensation reaction products herein usually contain two ormore labile hydrogen atoms. In those reaction products containing onelabile hydrogen, one or more easily substitutable or replaceable atom orgroup, for example a bath-compatible, water-solubilizing cation, e. g.,Na, K or NH are also linked in the reaction product molecule.

The prior nickel plating baths which are improved upon by the presentinvention contain water as solvent or continuous phase, and nickel ionsin the form of the sulfate,

sulfamate or fiuoborate of nickel. In addition these acid baths usuallycontain chloride ions, for instance as nickel chloride, for anodecorrosion; boric acid; one or more stabilizers such as for instance,saccharine, para-toluene sulfonamide, hexylammine and cyanuric acid; oneor more brighteners, for instance an alcohol or an unsaturated aldehyde;and one or more wetting agents, for instance lauryl sulfate.

The naphthosultones undergo the condensation reaction with theheterocyclic aromatic compounds hereafter set forth containing one ormore five-membered rings including one or more ring nitrogen atoms andone or more labile hydrogen atoms to form the new and valuablecondensation reaction products, in a molar ratio within the range ofabout 1-4 moles of the naphthosultone per mole of such heterocyclicaromatic compound. Such heterocyclic aromatic compounds include, forexample, an indolinine, e.g., indolinine per se, of the formula:

a fi-nitrosoindole of the formula:

wherein M is a bath-compatible, water-solubilizing cation, e.g., Na, Kor NH; a phthalocyanine, e.g., phthalocyanine per se, of the formula:

Q? IL: NH N N go a dimethyl-1,5-imidazole, e.g., dimethyl-1,5-imidazoleper se, of the formula:

and its substitution derivative, porphyrins; and a succinimide e.g.succinimide per se, of the formula:

All of such heterocyclic aromatic compounds are obtainable in commerce.Such heterocyclic aromatic compounds contain in addition to carbon,hydrogen and nitrogen, typically up to four five-membered heterocyclicrings of the character previously described herein, either as such orfused to six-member aromatic rings. The naphthosultones herein,preparable by the intramolecular condensation of the correspondinghydroxynaphthalene sulfonic acid, are also obtainable in commerce.

In place of the known brighteners, the novel condensation reactionproduct or products of naphthosultones and acetylenically-unsaturatedglycols can be added to the bath as brightener. Such brighteners aredisclosed and claimed in copending U.S. Patent application Ser. No.500,462, entitled Nickel Electroplating Baths and Novel CondensationReaction Products of Naphthosulfones and Acetylenically UnsaturatedGlycols as Brighteners Therefor, filed Oct. 1, 1965.

The novel condensation reaction product herein is added to the batheither as such or when combined with an inert, i.e., non-reactive withthe constituents of the bath, liquid solvent in an amount within therange from about 5-600 milligrams per liter.

The bath herein is preferably used with mechanical cathode rodagitation; a bath temperature between about 20 C. and about 70 C., morepreferably between about 55 C. and about 70 C.; a pH of the bath between3.0 and 5.5, more preferably about 5.0; and a current density between 2and 15 amps./dm. the optimum being between 3 and 7 amps./dm. for a bathhaving a temperature of the order of 65 C.

When the novel condensation reaction product herein is utilized as asolution in an inert, i.e., non-reactive with respect the constituentsof the plating bath, liquid solvent, the solvent can be water. Howeverany inert liquid solvent which is compatible with the plating bath canbe utilized. The proportions of the condensation reaction product insuch additive agent composition can be varied over wide limits, and donot form a part of this invention. It will suffice to point out thatwith higher concentrations of the condensation reaction product, smallerquantities of such addition agent composition are required to be addedto the bath to obtain the desired concentration of such product withinthe range from about 5-600 milligrams per liter, than when lowerconcentrations of the condensation reaction product are present in theadditive agent composition.

In its broader aspects, the preparation process for preparing thecondensation reaction products herein comprises reacting in an aqueoussystem under acid conditions and at a reaction temperature anaphthosultone, for instance a naphtho-1,8-sultone, with theheterocyclic aromatic compound containing one or more five-memberedheterocyclic rings including one or more ring nitrogen atoms and one ormore labile hydrogen atoms.

More specifically the preparation process involves heating an aqueousliquid admixture of the naphthosultone and such heterocyclic aromaticcompound in amount which is at least that required to stoichiometricallyreact with the naphthosultone to form the condensation reaction product,at an acid pH, preferably a pH of about 354.0, to an elevatedtemperature below 65 C., preferably of the order of 50 C., andmaintaining the admixture at such temperature below 65 C. until thenaphthosultone dissolves in the aqueous liquid. The thusobtained liquid.solution is then heated to a reaction temperature above 65 C. but below100 C., preferably of the order of C. and maintained at the reactiontemperature within the range aforesaid until the solution thickens,i.e., its viscosity is increased appreciably, and becomes of syrupyconsistency. The thus-obtained mixture or solution is then cooled, toambient or room temperature, for instance by being permitted to cooldown or by indirect heat exchange with a cooling fluid, e.g., coolingwater.

For a better understanding of the invention, the following examples ofnickel baths are given according to the Example No 1 2 3 4 5 6 7 NiSO-7HO 330 380 330 330 380 0 Ni suliamate 0 0 0 0 0 450 400 NiCl-(SHO 8045 80 80 45 30 30 2B O 3 40 40 40 40 40 50 50 Saccharin. 0. 1 0. 0. 1 0.2 0. 5 0. 2 0. 2 Paratoluen sulionanndeu 0. 1 0. 1 0. 1 0. 1 0. 1 0. 10. 1 Cyanuric acid 0. l 0 0. 1 0. 3 0 0. l 0. 1 Brlghtener A 0. 2 0. 2 00 0. 3 0. 2 0 Brlghtener 0 0 0. 2 0. 1 0 0 0. 2 Compound A- 0. 05 0 0 00. 04 0. 05 0 Compound B- 0 0.025 0 0 0 0.05 0 Compound C 0. 02 0 0 0.05 0 0 0. 10 Compound D 0 0. 05 0 0. 025 0. 02 0 0 Compound E 0 0 0. 10. 05 0 0 0 Compound F... 0 0 0. 05 0 0 0 0 Compound G 0 0 0 0 0. 01 0 0pH 4.0 3.5 4.5 4.0 4.0 3.5 3.5 Temperature 55-70 55-70 60 55-70 55-7040-68 60 2-7 2-7 2. 7 2-7 2-7 15 Current density (amps/ Brightener A wasbutynediol.

Brightener B Was the product of the equimolar condensation reaction ofbishydroxyethylether of the hutynediol with naphtlro-LS-sultone.

The Compounds A to G in the Examples of the preceding table aredesignated the following herein and are obtained by the condensationreaction of the reactants stated:

Compound A.Indolinine naphtha-1,8 sultone, resulting from the equirnolarreaction of indolinine and of naphtho-1,8 sultone. Optimum quantity ofCompound A is 10-500 mg./1.

Compound B.Indole-B-isonitroso naphtho-l,8 sultone, resulting from theequimolar reaction of fl-nitroso indole and naphto-1,8 sultone. Optimumquantity of Compound B is 5-500 mg./l.

Compound C.-Phthalocyanine nap'htho-1,8 sultone, resulting from thereaction of one mole of phthalocyanine and four moles of naphtho-1,8sultone. Optimum quantity of Compound C is 10-300 mg./l.

Compound D.-Dimethyl-1,5 imidazole naphtha-1,8 sultone, resulting fromthe equimolar reaction of dimethyl- 1,5 imidazole and naphtho-l,8sultone. Optimum quantity of Compound D is -600 mg./l.

Compound E.-Porphine naphtho-1,8 sultone, resulting from the reaction ofone mole of porphine and two moles of naphtho-1,8 sultone. Optimumquantity of Compound E is 1 0-150 mg./l.

Compound F.-Porphyrine naphtha-1,8 sultone, resulting from the reactionof one mole of porphyrine (substituted porphine) and two moles ofnaphtho-l,8 sultone. Optimum quantity of Compound -F is the same as E.

Compound G.Su-ccinimide naphthol,8 sultone, resulting from the equimolarreaction of succinimide and naphtho-1,8 sultone. Optimum quantity ofCompound G is 50-500 mg./ 1.

The preparation of Compounds A to G is carried out by the followingexemplary procedure:

In a reflux apparatus is placed in stoichiometric proportions (forexample, equimolar in the case of Compounds A, B, D and G), thepentagonal, nitrogen-containing heterocyclic compound containing thelabile hydrogen, and then the sultone is added to the pentagonalheterocyclic compound. Water is then added as is acid, such as HCl, tobring the pH to 3.5-4.0. The resulting mixture is heated at firstprogressively to 50 C. until the sulfone dissolves and then the mixtureis 'heated to approximately 85 C. The mixture is then held at about 85C. for about four hours. The viscosity of the liquid rises and itbecomes syrupy. The mixture is then cooled to ambient or roomtemperature.

The solution thus-obtained can be used directly as a levelling agentunder conditions specified above. Baths containing a levelling agentaccording to the invention give nickel deposits, which are adherent,ductile and virtually perfectly levelled, without pits or porosity.

What is claimed is:

1. An aqueous acidic nickel electrodepositing bath containing a sourceof nickel ions and as a levelling agent the condensation reactionproduct of naphtho-hS-sultone with a heterocyclic aromatic compoundcontaining at least one five-membered heterocyclic ring including atleast one ring nitrogen atom and at least one labile hydrogen atom andprepared by heating an aqueous liquid admixture of the naphthosultoneand the heterocylic aromatic compound present in at least astoichiometric amount under acid conditions to a reaction temperatureabove 65 C. but below C., maintaining the liquid admixture at a reactiontemperature within the range aforesaid until the viscosity of the liquidincreases appreciably and the liquid is of a syrupy consistency, andthereafter cooling the liquid admixture to room temperature, thecondensation reaction product being present in the bath in an amountsufficient to yield levelled nickel electrodeposits.

2. The bath of claim 1 wherein the naphtho-1,8-sultone and theheterocyclic aromatic compound are reacted together at the reactiontemperature maintained above 65 C. but below 100 C. in a molar ratiowithin the range of about 1-4 moles of the naphthosultone per mole ofthe heterocyclic aromatic compound.

3. An aqueous acidic nickel electroplating bath containing a source ofnickel ions and as a levelling agent the condensation reaction productof naphtho-1,8-sultone with a heterocyclic aromatic compound containingat least one five-membered heterocyclic ring including at least one ringnitrogen atom and at least two labile hydrogen atoms and prepared byheating an aqueous liquid admixture of the naphthosultone and theheterocyclic aromatic compound present in at least a stoichiometricamount under acid conditions to an elevated temperature below 65 C.,maintaining the admixture at the elevated temperature below 65 C. untilthe naphthosultone dissolves in the aqueous liquid, then heating theresulting liquid solution to a reaction temperature above 65 C. butbelow 100 C., maintaining the solution at a reaction temperature above65 C. but below 100 C. until the viscosity of the liquid solutionincreases appreciably and the solution is of a syrupy consistency, andcooling the thus-treated solution to room temperature, the condensationreaction product being present in the bath in an amount sufficient toyield levelled nickel electrodeposits.

4. The bath of claim 3 wherein the heterocyclic aromatic compound is anindolinine.

-5. The bath of claim 3 wherein the heterocyclic aromatic compound is aB-nitrosoindole.

6. The bath of claim 3 wherein the heterocyclic aromatic compound is aphthalocyanine.

7. The bath of claim 3 wherein the heterocyclic aromatic compound is adimethyl-1,5-imidazole.

8. The bath of claim 3 wherein the heterocyclic aromatic compound isselected from the group consisting of porphine and porphyrins.

9. The bath of claim 3 wherein the condensation reaction product ispresent in the bath in amount from about 5-600 m'g./l.

10. The bath of claim 3 wherein the pH of the bath is between 3.0 and5.5.

11. The bath of claim 3 wherein the aqueous liquid admixture of thenaphthosultone and heterocyclic aromatic compound is at a pH of about3.5-4.0 during the heating thereof to an elevated temperature below 65C.

12. A composition well suited as a levelling additive for a nickelelectroplating bath comprising a solution in an inert liquid solvent ofthe condensation reaction product of naphtho-1,8-sultone with aheterocyclic aromatic compound containing at least one five-memberedheterocyclic ring including at least one ring nitrogen atom and at leastone labile hydrogen atom and prepared by heating an aqueuos liquidadmixture of the naphthosultone and the heterocyclic aromatic compoundpresent in at least a stoichiometric amount under acid conditions to areaction temperature above 65 C. but below 100 C., maintaining theliquid admixture at a reaction temperature within the range aforesaiduntil the viscosity of the liquid increases appreciably and the liquidadmixture is of a syrupy consistency, and thereafter cooling the liquidadmixture to room temperature.

13. The composition of claim 12 wherein the five-membered heterocyclicring contains at least two labile hydrogen atoms.

14. The composition of claim 12 wherein the acqueous liquid admixture ofthe naphthosultone and heterocyclic aromatic compound is at a pH ofabout 3.5-4.0 during the heating thereof to a reaction temperature above65 C. but below 100 C.

15. In a method for the electro-depositing of nickel, the improvementwhich comprises effecting the nickel electrodeposition from an aqueousacidic nickel electrodepositing bath containing a source of nickel ionsand as a levelling agent a bath-campatible condensation reaction productof naphtho-1,8-sultone with a heterocyclic aromatic compound containingat least one five-membered heterocyclic ring including at least one ringnitrogen atom and at least one labile hydrogen atom and prepared byheating an aqueous liquid admixture of the naphthosultone and theheterocyclic aromatic compound present in at least a stoichiometricamount under acid conditions to a reaction temperature above 65 C. butbelow 100 C., maintaining the liquid admixture at a reaction temperaturewithin the range aforesaid until the viscosity of the liquid increasesappreciably and the liquid is of a syrupy consistency, and thereaftercooling the liquid admixture to room temperature, the condensationreaction product being present in the bath in an amount sufiicient toyield levelled nickel electrodeposits.

16. In a method for the electroplating of nickel, the improvement whichcomprises effecting the nickel electroplating from an aqueous acidicnickel electroplating bath containing a source of nickel ions and as alevelling agent a bath-compatible condensation reaction product ofnaphtho-1,8-sultone with a heterocyclic aromatic compound containing atleast one five-membered heterocyclic ring including at least one ringnitrogen atom and at least two labile hydrogen atoms and prepared byheating an aqueous liquid admixture of the naphthosultone and theheterocyclic aromatic compound present in at least a stoichiometricamount under acid conditions to an elevated temperature below C. untilthe naphthosultone dissolves in the aqueous liquid, then heating theresulting liquid solution to a reaction temperature above 65 C. butbelow C., maintaining the solution at a reaction temperature above 65 C.but below 100 C. until the viscosity of the liquid solution increasesappreciably and the solution is of a syrupy consistency, and cooling thethus-treated solution to room temperature, the condensation reactionproduct being present in the bath in an amount sufficient to yieldlevelled nickel electrodeposits.

References Cited UNITED STATES PATENTS 1,564,414 12/1925 Hoff 204-501,915,334 6/1933 Salzberg et al. 260-243 2,075,359 3/1937 Salzberg et al16722 2,469,727 5/1949 Hoffman 20449 2,849,352 8/1958 Kirstahler et al.20449 XR 2,850,507 9/1958 Gaertner 260327 2,876,177 3/1959 Gundel et al20449 3,122,490 2/1964 Strauss 20449 FOREIGN PATENTS 622,565 6/1961Canada. 868,898 5/1961 Great Britain.

JOHN H. MACK, Primary Examiner.

G. KAPLAN, Assistant Examiner.

US. Cl. X.'R. 260326, 309, 314.5

